DESCRIPTION FEATURES APPLICATIONS TYPICAL APPLICATION

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1 LTC-./LTC- Step-p/Step-Down Switched Capacitor DC/DC Converters with Low-Battery Comparator FEATRES.V or V Output Voltages V to V Input Voltage Range p to ma Output Current Only Three External Capacitors Required Soft Start Limits Inrush Current at Turn-On Low Operating Current: µa Low Shutdown Current: µa Shutdown Disconnects Load from Short-Circuit and Overtemperature Protected khz Switching Frequency Low-Battery Comparator Active in Shutdown Available in SO- Package APPLICATIONS Battery-Operated Equipment Smart Card Readers Local Power Supplies Handheld Instruments Battery Backup Supplies DESCRIPTION The LTC -./LTC- are micropower switched capacitor DC/DC converters that produce a regulated output voltage by either stepping up or stepping down the input voltage. Output voltage is fixed at either.v (LTC-.) or V (LTC-) by an internal resistor divider. A unique architecture allows the parts to accommodate a wide input voltage range (V to V) while maintaining ±% regulation. Additional circuitry prevents excessive inrush current and output voltage ripple when large to differentials are present. An internal uncommitted comparator is kept active in shutdown. The comparator has an open-drain output for flexible interfacing. The parts are short-circuit and overtemperature protected. Battery life is maximized by very low operating currents (I CC = µa typ, µa in shutdown). Both parts are available in an SO- package., LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATION V Step-p/Step-Down Power Supply with Low-Battery Detect LTC- Output Voltage vs Input Voltage LOW BAT.M 99k k LTC- C C.µF = V I OT = ma TA -CELL NiCd OTPT VOLTAGE (V)....9 I OT = ma. 9 LT TA

2 LTC-./LTC- ABSOLTE MAXIMM RATINGS W W W (Note ) to....v to V to....v to V,, to....v to V Short-Circuit Duration... Indefinite Operating Temperature Range Commercial... C to C Industrial... C to C Storage Temperature Range... C to C Lead Temperature (Soldering, sec)... C PACKAGE/ORDER INFORMATION TOP VIEW C C S PACKAGE -LEAD PLASTIC SO T JMAX = C, θ JA = C/ W W ORDER PART NMBER LTCCS-. LTCCS- LTCIS-. LTCIS- S PART MARKING I I Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS = V to V, = V, C =.µf, C IN = C OT =, unless otherwise noted (Note ). PARAMETER CONDITIONS MIN TYP MAX NITS Operating Voltage LTC-.. V LTC-. V (LTC-.) V V, I OT ma... V V V, I OT ma... V (LTC-).V V, I OT ma.. V.V V, I OT ma.. V Operating Current V, I OT =, = V µa > V, I OT =, = V µa Shutdown Current = V, V µa = V, > V µa Output Ripple Full Load (Note ) mv P-P Switching Frequency khz Trip Point Ramping Negative... V Trip Point Hysteresis % Input Current =.V na V OL I SINK = µa, = V.. V Leakage Current V = V, = µa Input Threshold V IL. V V IH. V Input Current = µa = V µa I OT Short-Circuit Current = V ma t ON Soft Start Turn-On Time ms The denotes specifications which apply over the full operating temperature range. Note : Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note : For V, C OT = µf.

3 LTC-./LTC- TYPICAL PERFORMANCE CHARACTERISTICS W EFFICIENCY (%) OTPT VOLTAGE RIPPLE (mv P-P ) LTC-. Efficiency vs Output Current.. OTPT CRRENT (ma) =.V T A = C = V =.V =.V = V G LTC- Output Voltage Ripple vs Input Voltage = V I OT = ma T A = C C OT = µf C OT = C OT = µf EFFICIENCY (%) OTPT VOLTAGE (V) LTC- Efficiency vs Output Current =.V = V =.V = V = V T A = C.. OTPT CRRENT (ma)..... LTC-. Output Voltage vs Input Voltage =.V C OT = T A = C G OTPT VOLTAGE RIPPLE (mv P-P ) OPERATING CRRENT (µa) LTC-. Output Voltage Ripple vs Input Voltage =.V I OT = ma T A = C C OT = C OT = µf C OT = µf LTC- Operating Current vs Input Voltage = V I OT = ma C C C G. G G G EFFICIENCY (%) LTC-. Efficiency vs Input Voltage =.V I OT = ma T A = C EFFICIENCY (%) LTC- Efficiency vs Input Voltage = V I OT = ma T A = C SHTDOWN SPPLY CRRENT (µa) LTC-X Shutdown Supply Current vs Input Voltage = V C C C G G G9

4 LTC-./LTC- TYPICAL PERFORMANCE CHARACTERISTICS W LTC- Step-Down Mode Load Transient Response LTC- Step-p Mode Load Transient Response AC COPLED mv/div AC COPLED mv/div I OT ma/div ma ma I OT ma/div = V, = V, C OT =, T A = C G =.V, = V, C OT =, T A = C G BLOCK DIAGRAM W C C STEP-P/STEP-DOWN CHARGE PMP khz OSCILLATOR.V V REF BD PIN FNCTIONS (Pin ): Shutdown Input. A logic low on the pin puts the part into shutdown mode. A logic high (V.V) enables the charge pump regulator. At high voltages, the pin may still be controlled with V logic without causing a large rise in quiescent current. The pin may not float; connect to if unused. (Pin ): Open-Drain, Low-Battery Comparator Output. This pin will pull low whenever the voltage on the pin is less than the internal reference voltage (.V typ). (Pin ): Low-Battery Comparator Input. The voltage on this pin is compared to the internal reference voltage (.V). The output will sink current when the voltage on the pin is less than.v typ. The low-

5 LTC-./LTC- PIN FNCTIONS battery comparator and.v reference are kept alive in shutdown. (Pin ): Ground. Should be tied to a ground plane for best performance. C (Pin ): Charge Pump Flying Capacitor, Negative Terminal. C (Pin ): Charge Pump Flying Capacitor, Positive Terminal. APPLICATIONS INFORMATION Regulator Operation W The regulator section of the LTC-./LTC- consists of a charge pump, reference, comparator and some logic. The divided down output voltage is compared to the internal reference voltage. When the divided output drops below the reference voltage, the charge pump is enabled, which boosts the output back into regulation. Hysteresis in the comparator forces the regulator to burst on and off and causes approximately mv of peak-to-peak ripple to appear at the output. By enabling the charge pump only when needed, the LTC-. and LTC- are able to achieve high efficiencies with low output load currents. Each part s charge pump has a unique architecture that allows the input voltage to be either stepped up or stepped down to produce a regulated output. Internal circuitry senses the to differential voltage and controls the charge pump operating mode. In addition, the effective output impedance of the charge pump is internally adjusted to prevent large inrush currents and allow for a wide input voltage range. When the input voltage is lower than the output voltage, the charge pump operates as a step-up voltage doubler. When the input voltage is greater than the output, the charge pump operates as a step-down gated switch. Capacitor Selection For best performance, low ESR capacitors are recommended for both C IN and C OT to reduce noise and ripple. The C IN and C OT capacitors should be either ceramic or (Pin ): Charge Pump Input Voltage. May be between V and V (LTC-.) or between.v and V (LTC-). should be bypassed with a low ESR capacitor as close as possible to the pin for best performance. (Pin ): Regulated Output Voltage. The output voltage is internally set to either.v (LTC-.) or to V (LTC-) using an internal resistor divider. should be bypassed with a low ESR capacitor as close as possible to the pin for best performance. tantalum and should be or greater. If the input source impedance is very low (<.Ω), C IN may not be needed. Increasing the size of C OT to µf or greater will reduce output voltage ripple particularly with high voltages (V or greater). A ceramic capacitor is recommended for the flying capacitor C with a value of.µf or.µf. Smaller value flying capacitors may be used in low output current applications. Output Ripple Normal LTC-./LTC- operation produces voltage ripple on the pin. Output voltage ripple is required for the parts to regulate. Low frequency ripple exists due to the hysteresis in the sense comparator and propagation delays in the charge pump enable/disable circuits. High frequency ripple is also present mainly from the ESR (equivalent series resistance) in the output capacitor. Typical output ripple ( < V) under maximum load is mv peak-to-peak with a low ESR (<.Ω) output capacitor. For applications requiring to exceed V, a µf or larger C OT capacitor is recommended to maintain max ripple in the mv range. The magnitude of the ripple voltage depends on several factors. High input voltages increase the output ripple since more charge is delivered to C OT per charging cycle. A large C flying capacitor (>.µf) also increases ripple in step-up mode for the same reason. Large output current load and/or a small output capacitor (<) results in higher ripple due to higher output voltage dv/dt. High ESR capacitors (ESR >.Ω) on the

6 LTC-./LTC- APPLICATIONS INFORMATION W output pin cause high frequency voltage spikes on with every clock cycle. There are several ways to reduce the output voltage ripple. A larger C OT capacitor (µf or greater) will reduce both the low and high frequency ripple due to the lower C OT charging and discharging dv/dt and the lower ESR typically found with higher value (larger case size) capacitors. A low ESR ceramic output capacitor will minimize the high frequency ripple, but will not reduce the low frequency ripple unless a high capacitance value is chosen. A reasonable compromise is to use a to µf tantalum capacitor in parallel with a µf to.µf ceramic capacitor on to reduce both the low and high frequency ripple. An RC or LC filter may also be used to reduce high frequency voltage spikes (see Figure ). LTC-X LTC-X Inrush Currents µf TANTALM Ω TANTALM µf CERAMIC TANTALM F Figure. Output Ripple Reduction Techniques A common problem with switched capacitor regulators is inrush current particularly during power-up and coming out of shutdown mode. Whenever large (or boosted ) to voltage differentials are present, most charge pumps will pull large current spikes from the input supply. Only the effective charge pump output impedance limits the current while the charge pump is enabled. This may disrupt input supply regulation, especially if the input supply is a low power DC/DC converter or linear regulator. The LTC-./LTC- minimize inrush currents both at start-up and under normal high to operation. Internal soft start circuitry controls the rate at which may be charged from V to its final regulated value. The typical start-up time from = V to V is ms. This corresponds to an effective charging current of only.ma for a output capacitor (.ma for µf, etc). Note that any output current load present during start-up will add directly to the charging currents mentioned above. The soft start circuitry limits start-up current both at initial power-up and when coming out of shutdown. As the (or boosted ) to voltage differential grows, the effective output impedance of the charge pump is automatically increased by internal voltage sensing circuitry. This feature minimizes the current spikes pulled from whenever the charge pump is enabled and helps to reduce both input and output ripple. Protection Features The LTC-X contain thermal shutdown and shortcircuit protection features. The parts will shut down when the junction temperature reaches approximately C and will resume operation once the junction temperature has dropped back to approximately C. The parts will limit output current to ma (typ) when a short-circuit condition ( < mv) exists. The parts can survive an indefinite short to. The LTC-X devices use a low thermal resistance SO- package ( C/W vs C/W for standard SO-). This permits full output current, even at high input supply voltages. Low-Battery Comparator The internal low-battery comparator trips at. ±% ( ramping negative). Programming the comparator to trip at a higher voltage can easily be done with an external V BAT R R LTC-X C C F V TRIP =.V( R/R) ( RAMPING NEGATIVE) Figure. Programming the Low-Battery Comparator Trip Voltage

7 LTC-./LTC- APPLICATIONS INFORMATION W resistor divider (see Figure ). Since the low-battery comparator is kept alive in shutdown, it may be used to protect batteries against deep discharge by shutting down the power supply when the battery voltage gets too low. The open-drain comparator output allows for flexible interfacing between the output and external logic. pull-up resistors in the k to M range are recommended. TYPICAL APPLICATIONS N.V Step-p/Step-Down Supply with Power Good Output POWER GOOD k k LTC-. V V TRIP C 99k C.µF =.V ±% I OT = ma, > V V I OT = ma, > V IN V TO V TA Low Power Battery Backup Supply with Autoswitchover and No Reverse Current MAIN V SPPLY BACKED-P CIRCITRY TPT.M 99k 99k.V V TRIP 99k LTC- C C V BACKP SPPLY I OT = ma.µf BAT TRICKLE CHARGE AND LTC I DD -CELL NiCd BATTERY TA Battery/External Power Autoswitch Regulator V WALL ADAPTER INPT M 99k MBRL LTC- C C.µF 99k CHARGE PATH µf -CELL NiCd BATTERY EXTERNAL POWER GOOD V TA Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

8 LTC-./LTC- TYPICAL APPLICATIONS N Low Power Dual Output Supply (Maximum Combined I OT = ma) Ω Q k.v ±% Q k k.nf k LTC- C C.µF µf V ±%.V TO V Q: TPT Q: MMBT9LT TA Step-p/Step-Down Power Supply with Input Autoswitching CENTRAL SEMI CMPDC WALL ADAPTER VDC Si9DQ MMBZ BLT (.V) k Si9DQ Si9DQ AAA ALKALINE CELLS EXT_PWR_GOOD MMBD 9LT.k k k k M k MMBT 9LT N V MMBT 9LT LTC- C C.µF µf V V ma TA PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. RELATED PARTS PART NMBER DESCRIPTION COMMENTS LTC Series Step-p/Step-Down Switched Capacitor DC/DC Converters with Reset V to V,.V, V and ADJ Versions, I OT to ma LTC Micropower, Regulated V Charge Pump DC/DC Converter I OT = ma ( V), I OT = ma ( V) LTC- Micropower, Regulated V Charge Pump DC/DC Converter LTC Without Shutdown and Packaged in SOT- LTC Micropower, Regulated V Charge Pump DC/DC Converter Available in -Pin MSOP, µa Quiescent Current, I OT = ma LTC/LTC SIM Power Supply and Level Translators Step-p/Step-Down SIM Power Supply and Level Translators LTC ma CMOS Voltage Converter V to V Conversion with Low Voltage Loss.. (..).. (..).... TYP..9 (..)..9 (..) *DIMENSION DOES NOT INCLDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED." (.mm) PER SIDE ** DIMENSION DOES NOT INCLDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED." (.mm) PER SIDE Linear Technology Corporation McCarthy Blvd., Milpitas, CA 9- () -9 FAX: () - TELEX: S Package -Lead Plastic Small Outline (Narrow.) (LTC DWG # --). (.) TYP.. (..).. (.9.9).9.9* (..)..** (..9) SO 99 f LT/TP 9 K PRINTED IN SA LINEAR TECHNOLOGY CORPORATION 99